1. Field of the Invention
The present invention relates to a grommet and particularly to a grommet that can be assembled onto a wiring harness and mounted in a through hole in a body panel of an automotive vehicle. The grommet protects the wiring harness and makes a portion where the wiring harness introduced into the through hole waterproof, dustproof and soundproof.
2. Description of the Related Art
A grommet typically is mounted on a wiring harness that will extend from an engine compartment to a passenger compartment of an automotive vehicle. The grommet and the wiring harness than are mounted in a through hole of a body panel that partitions the engine compartment from the passenger compartment. Accordingly, the grommet protects the wiring harness at the through hole and prevents the flow of water, dust and sound from the engine compartment to the passenger compartment.
A grommet of the type described above is referred to as a xe2x80x9cone-motion grommetxe2x80x9d and has a body-locking recess around its outer periphery. The body locking recess is configured to be engaged with the surrounding edge of a through hole of a body panel merely by pushing the grommet into the through hole in one direction. A one-motion grommet has the potential for easy mounting.
A known one-motion grommet is disclosed in Japanese Unexamined Utility Model Publication No. 4-42982 and also is identified by the numeral 1 in FIG. 10 herein. The grommet 1 has small-diameter tubes 2 and 3 at opposite ends of the grommet 1 and a widened tube 4 between the small-diameter tubes 2 and 3. A body locking recess 5 is formed in the outer circumferential surface of the widened tube 4, and a cut-away portion 6 is formed at the radially inner side of the body locking recess 5.
The grommet 1 is pushed in the direction of arrow Q from an engine compartment (X) to a passenger compartment (Y). As a result, a slanted wall 5a of the body locking recess 5 is deformed inwardly into the cut-away portion 6, and is enabled to pass through a through hole 9 formed in a body panel 8. The slanted wall 5a is restored to its original shape after passing through the through hole 9, so that the body panel 8 is locked between the slanted wall 5a and another side wall 5b. 
The cut-away portion 6 extends from an opening 6a beyond a position radially inwardly of the body locking recess 5 to facilitate the inward deformation of the slanted wall 5a when the grommet 1 is being pushed into the through hole 9. The cut-away portion 6 then is bent radially outwardly beyond the body locking recess, so that a back end 6b of the cut-away portion 6 reaches substantially the same radial position as a groove bottom surface 5c of the body locking recess 5.
The base of the slant wall 5a is thinner at its outer circumference than at its inner circumference. As a result, the cut-away portion 6 is likely to cause the slanted wall 5a to deform outwardly when the body panel 8 contacts an outer circumferential surface 4a of the widened portion 4 adjacent the back end 6b of the cut-away portion 6. Deformation of the slanted wall 5a outwardly instead of inwardly will cause the slanted wall 5a to abut against a wall surface 8a of the body panel 8 at the side from which the grommet 1 is pushed, as shown in FIG. 4(B). Hence, it will be difficult to insert the grommet 1 into the through hole 9. More particularly, the cut-away portion 6 that is formed to facilitate the inward deformation of the slanted wall 5a may actually cause the slanted wall 5a to deform outwardly and in a direction opposite from the desired direction. This complicates the insertion of the grommet 1 into the through hole 9 and requires a larger insertion force.
The through hole of the body panel may be oblong. However, the small diameter tube is usually circular. As a result, the cut-away portion 6 may be large along one axis and small along a second axis. If the cut-away portion is excessively large along the longer axis, the surrounding wall where the body locking recess is formed enters the cut-away portion. Consequently, the body locking recess may pass through the through hole.
The cut-away portion is formed inside the side wall of the body locking recess to facilitate the inward deformation of the side wall of the recess. However, the side wall may be inclined excessively inwardly to cause the body locking recess to pass through the through hole both when the grommet is pushed into the through hole of the body panel, and when the grommet is pulled through the through hole. This may occur when the through hole is oblong and the widened tube portion formed with the body locking recess is circular, and when the through hole and the widened tube portion are both circular.
In view of the above problems, an object of the invention is to improve a mount ability of a grommet by causing a side wall of a body locking recess to be easily and securely deformed inwardly during insertion of a grommet into a through hole in a body panel.
The invention is directed to a grommet that is insertable into a through hole in a body panel in one direction, and that can be engaged with the through hole while mounted on a wiring harness. The grommet may be unitarily formed from a rubber or elastomer, and comprises first and second small-diameter tubes at opposite longitudinal ends of the grommet. The first small-diameter tube defines the front of the grommet with respect to the insertion direction of the grommet into the through hole, and hence the second small diameter tube defines the rear end of the grommet.
The grommet further comprises a widened tube between the first and second small-diameter tubes. The widened tube includes a cut-away portion that extends forward into the rear end of the widened tube and that opens toward the rear end of the grommet. Thus, the cut-away portion branches the widened tube into an outer tube and an inner tube. The inner tube is substantially continuous with the second small-diameter tube.
A body locking recess is defined in the outer tube. The body locking recess is more backward than the forward end of the cut-away portion along the longitudinal direction of the grommet. Additionally, the forward end of the cutaway portion preferably is more radially inward than the radially inward bottom end of the body locking recess. Thus, at least a portion of the outer tube will deform inwardly toward the cut-away portion in response to forces exerted by the body panel on the insertion side of the outer tube while the grommet is being pushed into the through hole in the body panel.
The body locking recess preferably is defined partly by front and rear projections on the outer surface of the outer tube. The front projection has a forwardly and outwardly facing slanted surface and a substantially radially aligned rearwardly facing surface that defines the forward side of the body locking recess. At least the forward end of the cut-away portion preferably is more radially inward than the slanted surface. These relative positions ensure that at least a portion of the outer tube will deform inwardly toward the cut-away portion in response to forces generated by the body panel on the slanted surface of the outer tube as the grommet is being pushed into the through hole in the body panel. Thus, unlike the above-described prior art, there is no possibility that the slanted surface of the annular front wall will deform radially outward in response to forces exerted by the body panel as the grommet is urged into the through hole. Accordingly, insertion of the grommet into the through hole is carried out smoothly.
The back end of the cut-away portion preferably has an opening side with an outer circumferential surface that is flared outwardly to widen toward the opening end of the cut-away portion. The outwardly flared surface preferably is radially inward from the annular rear wall of the outer tube. The base end of the slanted surface that contacts the body panel when the grommet is pushed into the through hole preferably is more radially outward than the back end of the cut-away portion. Accordingly, unlike the above-described prior art, there is no likelihood that the slanted surface is deformed outwardly against the body panel. Rather, the slanted wall is deformed inwardly toward the cut-away portion, thereby achieving a smoother pushing operation.
Further, the outer tube can be deformed easily toward the cut-away portion due to the widening at the back end opening of the cut-away portion. Therefore, the one-motion grommet can be mounted on the body panel with a small insertion force.
Portions of the outer tube adjacent the base end of the slanted surface preferably are thicker than portions of the inner tube substantially continuous with the second small-diameter tube. Thus, a pushing force of the body panel on the grommet first acts on the thinner inner tube to deform the inner tube when the body panel abuts against the slanted surface. The inward deformation of the inner tube then deforms the outer tube inwardly.
Portions of the inner tube branched by the cut-away portion and continuous with the second small-diameter tube are thinner than a base portion of the inner tube branched from the outer tube. Thus, when the body panel is brought into contact with the slanted surface of the projection that defines the body locking recess, the thinner portion of the inner tube first is pushed longitudinally thereby causing the thicker base portion to deform in a direction toward the center of the inner tube or radially inwardly and to cause the slanted wall of the outer tube to deform radially inwardly about the back end of the cutaway portion.
The grommet may further comprise an inclination-preventing projection on the outer circumferential surface of the inner tube along longitudinal direction to prevent the outer tube from inclining excessively. Thus, the outer tube comes into contact with the inclination-preventing projection to prevent the grommet from passing through the through hole.
The through hole of the body panel may be oblong. In this instance, the outer tube of the widened tube portion has an oblong cross section, but the inner tube through which the wiring harness is introduced has a substantially circular cross section. Thus, a clearance between the inner tube and the outer tube is widened at a longer axis side while being narrowed at a shorter axis side. Accordingly, the inclination-preventing projection is provided on the outer circumferential surface of the inner tube at the longer axis side, so that a distance between the projecting end of the inclination-preventing projection and the inner circumferential surface of the outer tube is substantially the same as a distance between the outer circumferential surface of the inner tube and the inner circumferential surface of the outer tube at the shorter axis side. Thus, the degree of deformation of the outer tube is restricted by the inclination-preventing projection to prevent the body locking recess from being deformed sufficiently inward to pass through the through hole of the body panel.
Most preferably, the inclination preventing projection projects a longer distance at the opening end of the cut-away portion.
Since the inward inclination of the outer tube is restricted, the projecting distance of the projection is made larger at a portion corresponding to an outwardly widened portion of the outer tube.
These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments.